Apple continues to dominate in tablet computers, although its market share is shrinking because of growing competition from Samsung and others, research firm IDC said Thursday.

Apple shipped 22.9 million iPads worldwide in the October-December quarter, during which it released a smaller version and updated its full-size models. That’s growth of 48 percent from the same period a year earlier. But IDC said Apple’s market share fell to 44 percent, from 52 percent.

Samsung Electronics, maker of the Galaxy line of devices, saw shipments more than triple to 7.9 million. Its market share more than doubled from 7.3 percent to 15.1 percent.

AsusTek Computer, maker of the Transformer line and Google’s Nexus 7, also saw shipments and market share increase.